There is no concern about running out of solar energy, in addition, the solar energy is environmentally-friendly clean energy. Accordingly, a solar power by use of the solar energy has been popular in recent years. Constituent members of a solar battery for use in a solar power generation system for generating a solar power will be described with reference to FIG. 11. FIG. 11 is a schematic diagram illustrating a relationship among an solar battery array 1010, a solar battery string 1001, solar battery modules 1011, and a solar battery cell 1000.
Note that, in the following description, the solar battery array, the solar battery string, the solar battery module, and the solar battery cell are abbreviated as the array, the string, the module, and the cell, respectively.
As illustrated in FIG. 11, the cell 1000 which receives radiation of sunlight to thereby generate an electric current with a photoelectric effect serves as a minimum unit of a solar battery. The module 1011 includes the plurality of cells 1000. The string 1001 is a string in which the plurality of modules 1011 are connected to each other in series. The array 1010 is an array in which the plurality of strings 1001 are connected to each other in parallel.
Next, an arrangement of a conventional solar power generation system will be schematically described with reference to FIG. 12. FIG. 12 is a block diagram illustrating a schematic configuration of the conventional solar power generation system 1100. As illustrated in FIG. 12, the solar power generation system 1100 includes an array 1010, a power conditioner 1020, and a load 1030. A direct-current power outputted from the array 1010 is inverted into an alternating-current power by an inverter 1021 included in the power conditioner 1020, and after that the alternating-current power is supplied to the load 1030.
Note that, as illustrated in FIG. 12, the solar power generation system 1100 is configured, for example, so as to operate in cooperation with a commercial electric power system 1040 provided by an electric power company, or alternatively, so as to operate as an independently system without cooperating with the electric power system 1040 of the electric power company.
An output of each of the cells 1000 is changed by various causes such as an installation state of the cells (e.g., angle of inclination), seasons (solar altitude), time (solar azimuth), weather (intensity of solar radiation (amount of solar radiation)), and/or temperatures. Therefore, even if an output of the solar power generation system is decreased, it is difficult to determine whether or not such decrease is caused by failure.